Burner control system



Aug. 4, 1942. F. s. DENISON BURNER CONTROL SYSTEM Filed Nov. 17, 1938 ihwmtor elm:

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Frederick $01) (Iitomeg Patented Aug. 4, 1942 BURNER CONTROL SYSTEM Frederick S. Denison, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Del- Application November 17, 1938, Serial No. 240,978

12 Claims.

The present invention is concerned with a burner control system and more particularly with one in which the pilot burner is lighted each time the system is placed in operation.

In fluid fuel burning systems, particularly gas burning systems, it is customary to provide a pilot burner for lighting the main burner. In the majority of gas burning systems, this pilot burner is constantly burning except during the summer months. In order, however, to eliminate the expense of having service men periodically relight the pilot burners, there has been an increasing tendency in recent years to employ systems in which the pilot burner is relighted each time that there is a call for burner operation.

An object of the present invention is to provide such a system wherein an electrical heating device is employed for igniting the pilot burner fuel and wherein the admission of fuel to the pilot burner is controlled by means responsive to the temperature of the heating device and the admission of fuel to the main burner is controlled by means responsive to the pilot burner flame temperature.

A further object is to provide a system according to the previous object in which the means responsive to the pilot burner flame is also operative upon the establishment of flame .to deenergize the heating device and cause the flow of the pilot burner to be maintained despite such de-energization of the heating device.

A still further object of the invention is to provide a burner employing an electric heater for heating the burner tube to a point that the fuel issuing therefrom is ignited and in which a device responsive to the expansion of the burner tube is employed for controlling the flow of fuel to said burner.

A still further object of the invention is to provide a burner control system embodying, as a pilot burner, a burner such as set out in the previous object and in which means responsive to the pilot burner flame operates a control device for the main burner valve and also holds the device responsive to expansion of the pilot burner tube in fuel admitting position so that upon deenergization of the heating means for the tube, the flow of fuel to the pilot burner is still maintained.

Other objects of the invention will be apparent from a consideration of the accompanying specification, claims and drawing.

In the single figure of the drawing, the burner control system is shown in schematic form.

Referring to the drawing, a portion of a gas burner is designated by the reference numeral III. This gas burner is supplied with gas through a pipe ll leading from a mixing chamber ll of conventional structure. Connected to the gas inlet of the mixing chamber I2 is a pipe l3 which communicates with the outlet of a valve H. The valve I4 is, in turn, connected to a gas pipe IS.

The valve 14 is shown as being of the electromagnetic type comprising a solenoid winding l6 and a solenoid core H which is secured to the valve proper. Secured to the upper end of the solenoid core I! is an extension I8 which is adapted to engage a pivoted switch carrier l9. Mounted on the switch carrier is a mercury switch 20. Upon energization of the electromagnetic winding IB, the solenoid core I1 is moved upwardly opening the valve and tilting the mercury switch 20. In the position of the mercury switch shown, the switch is closed. Upon tilting the same by energization of the solenoid, the mercury element moves to the right causing the switch to be opened.

The valve l4 functions as a main burner valve, controlling the flow of fuel to the main burner Ill.

The pilot burner is generally designated by the reference numeral 25. This pilot burner comprises a block of heat resistant insulating material 23 which is provided with a longitudinal bore 21 extending through nearly the full length thereof. Adjacent the right-hand end, however, the bore is reduced as at 28. At the point where the bore 21 is reduced, there is an inwardly projecting cylindrical flange 29. Secured to the left-hand end of block 26 is a closure block 30. This block is secured to block 26 by screws 3| or other similar fastening means. The block 30 is provided with a threaded aperture 32 in which a pipe 33 is screw-threadedly secured. The pipe 33 extends through the bore 21 and extends beyond the right-hand end of block 26. The pipe 33 communicates at its inlet end with a pipe 34 threaded into the left-hand end of block 30. The pipe 34 communicates with the outlet of a solenoid valve 35, the inlet of which is connected by means of a pipe 36 to the gas supply pipe l5. In order to clearly show the details of the pilot burner within the single view showing the system, I have shown the valves 35 and I4 together with the associated pipes I5 and 36 considerably reduced in size relative to the main and pilot burners and the equipment directly associated with them.

Pipe 33 is supplied with gas through passages 36 and 34 andfunctions as a pilot burner tube. The tube 33, for reasons to be discussed later, is preferably made of material having a relatively high temperature coefllcient of expansion. An electrical heating coil 33 has a portion thereof wound around the tube 33 and a second concentric portion thereof surrounding and coaxial with the flrst portion and engaging the outer wall of the bore 21. The outer coil portion is supported by the inwardly directed flange 26. The two pertions of the heating coil 36 serve to heat the tube 33 to a very high temperature so that gas issuing from tube 33 ignites as soon as it comes in contact with the atmosphere. This portion of the structure forms no part of the present invention, being disclosed in the patent to O. K. Beckler No. 1,981,299, granted November 20, 1934. The two ends of the heating conductor are connected to the screws 3|, which screws thus form terminal screws for the heating device.

Mounted in the block 26 are two contact screws 36 and 46. These screws are held in adjusted position by lock nuts 4| and 42. Cooperating with contacts 36 and 46 is a contact arm 44. Contact arm 44 is of relatively flexible material and carries contacts 45 and 46. Contacts 46 and 46 are more widely spaced from each other than the contacts 39 and 45 so that upon movement of contact arm 44 in contact making direction, contacts 36 and 45 are first moved into engagement and then upon further movement of the contact arm 44, contacts 46 and 46 will move into engagement. The contact arm 44 is pivotally mounted to a fixed support 41 at 46 and is provided with an upwardly extending arm 46. This arm is adapted to cooperate with a collar 56 rigidly secured to tube 33. On heating of tube 33 by means of the electrical heating element 36, the expansion of pipe 33 is transmitted through collar 56 to the vertical arm 49 to cause movement of contact arm 44 in a clockwise direction, as will be discussed in more detail later.

Secured to the flxed' support 41 is a U-shaped bimetallic element 52. One leg of the U-shaped bimetallic element 52 is secured to the support 41 and the other leg carries an arm 53 adapted to engage the contact arm 44 at a point adjacent the contact 46. The bowed portion of the bimetallic element 52 is adapted to lie in the path of a jet of the pilot burner flame. The main jet of the pilot burner is indicated in dotted lines by the reference numeral 55. The pilot burner is preferably provided with a slit not quite at the end thereof so as to produce an auxiliary flame 56, which auxiliary flame engages the bimetallic element 52. The bimetallic element is so disposed that upon being heated the arm 53 is moved upwardly thereby.

' A step-down transformer is generally indicated by the reference numeral 66. This transformer comprises a line voltage primary 6| and a low voltage secondary 62. The line voltage primary 6| is connected to line wires leading to a suitable source of power (not shown).

A room thermostat is generally designated by the reference numeral 64. This room thermostat is of conventional construction comprising a bimetallic element 65 to which is secured a contact arm 66 adapted to engage a fixed contact 61. Cooperating with the contact arm 66 is a magnet 63 which serves to impart a snap action to the movement of the arm 66. This snap action results in the elimination of sparking in the thermostat and also by requiring a temperature difl'erential between the opening and closing of the thermostat prevents excessively frequent operations of the equpment. While a room thermostat has been shown for purposes of illustration, it is to be understood that any other controlling switch may be used within the spirit of the invention.

Operation The various elements of the system are shown in the drawing in the positions they assume when the temperature to which thermostat 64 is responsive is at or above the desired value. The bimetallic element 65 of thermostat 64 is so arranged that upon a temperature decrease the arm 66 is moved to the left. Let it be assumed that the temperature falls to the point at which contact arm 66 engages contact 61. An energizing circuit will be established to the heating coil 36 as follows: from the left-hand terminal of secondary 62 through conductor 16, bimetallic element 65, contact arm 66, contact 61, conductors H and I2, mercury switch 26, conductor 13, lower terminal post 3|, heating coil 36, the upper terminal post 3|, and conductor 15 to the other terminal of secondary 62. The energizing of heating coil 36 causes the burner tube 33 to be heated up so that it gradually expands. Such expansion is transmitted through collar 56 and arm 46 to the contact arm 44. when the temperature of pipe 33 has risen to a point where gas flowing therethrough would be heated to a point such that it would ignite upon being exposed to the atmosphere, the expansion is sufllcient to cause contact arm 44 to effect engagement of contacts 46 and 39 so that the following circuit is established to the solenoid valve 35: from the left-hand terminal of secondary 62 through conductor 16, bimetallic element 65, contact arm 66, contact 61, conductors II and 11, contacts 45 and 36, conductor- 16, solenoid valve .35, and conductors l6 and 66 to the right-hand terminal of secondary 62.

The energization of solenoid 35, as a result of the above traced circuit, results in this valve being opened so that gas flows from the gas supply pipe l5 through pipe 36, valve 35, and pipe 34 to pipe 33. The gas flowing through pipe 33 is heated to a sufliciently high point that upon being admitted to the atmosphere it is immediately ignited. The jet 56 of the resulting pilot burner flame now engages the bimetallic element 52 causing the same to heat up and move arm 53 upwardly. The upward movement of arm 53 carries contacts 46 and 46 into engagement. Such upward movement also serves to hold contact arm 44 in a position in which contacts 36 and 45 are pressed flrmly into engagement independently of the position of collar 56. It is to be pointed out in this connection that the total expansion of tube 33, by reason of the heating action of heating element 36, is not sufllcient to cause contacts 46 and 46 to be moved into engagement. As soon as contacts 46 and 46 are moved into engagement by the action of the bimetallic element 52, a circuit is established to the winding l6 of the main burner valve I4 as follows: from the left-hand terminal of secondary 62 through conductor l6, bimetallic element 65, contact arm 66, contact 61, conductors II and 11, contact arm 44, conductors 46 and 46, conductor 62, winding l6, and conductors 63 and 66 to the right-hand terminal of secondary 62.

The establishment of the above traced energizing circuit to valve winding I6 causes valve M to be opened admitting gas to the main burner l6.

This gas is ignited by the pilot flame 55. It will be noted that the existence of the pilot flame 55 was assured before the valve I4 was opened so that there is no danger of gas being admitted to the burner l before there is a pilot flame to lgnite the same.

The energization of winding l6 also causes switch 20 to be tilted in a clockwise direction to efiect the opening thereof. The opening of switch 20 interrupts the previously traced circuit to heating coil 38 with a result that this heating coil is no longerenergized. It is obviously desirable to deenergize the heating coil since after the pilot burner has once been ignited, there is no further need for the continued energization of thesame. As a result of the heating coil being deenergized, the pilot burner tube 33 will cool down. Inasmuch, however, as the contacts 39 and 45 are held in engagement by the bimetallic element 52, the contraction of the tube 33 does not result in contacts 39 and 45 being separated. The valve 35 thus remains open until the thermostat 64 becomes satisfied or in other words,

until the temperature to which the thermostat 64 is exposed rises sufficiently to cause separation of the contact arm 86' from contact 61 against the holding force of magnet 68.

It is to be noted that all of the circuits to the various equipment are through the thermostat 64 so that upon this thermostat becoming satisfied, all of the apparatus is deenergized and the operation of the burner system is terminated. Similarly,'upon power failure, the system is completely shut down.

It will be noted that I have provided a burner control system employing an electrical heating device for igniting the pilot burner gas in which it is assured that no gas is admitted to the pilot burner until the heater is in condition for igniting the same and to the main burner until the pilot burner is definitely ignited. The system is thus entirely safe. over, accomplished in an extremely simple manner with a minimum of controlling equipment.

While I have shown a specific embodiment of my invention for the purpose of illustration, it is to be understood that the invention is limited only by the scope of the appended claims.

I claim as my invention:

1. In a fiuid fuel burner control system, a main fluid fuel burner, a pilot burner comprising a tube through which the fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coefiicient of expansion, means for heating said tube adjacent the open end thereof, means including a device responsive to the expansion of the tube for admitting fuel to the pilot burner only when the expansion of the tube is equal to that caused by a temperature sufiiciently high that the tube itself will cause ignition of the fuel passing therethrough as soon as it engages the atmosphere, and means including a device responsive to the temperature of the pilot burner flame operative when said pilot burner is ignited to cause fuel to be supplied to said main burner, to render said heating means ineffective, and to maintain said fuel flowing to said pilot burner in spite of the heating means being rendered ineffective.

2. In a fiuid fuel burner control system, a main burner, a pilot burner, an electrical heating device for igniting the fuel issuing from the pilot burner, electrically controlled main and pilot burner valves, first and second switches, a valve These features are, more-,

opening circuit for the pilot burner valve controlled by said first switch, a valve opening circuit for the main burner valve controlled by said second switch, means responsive to the temperature of the heating device for closing the first switch, and means responsive to the temperature of the pilot burner fiame for closing said second switch and holding said first switch in closed first switch, means responsive to the temperature (if the pilot burner fiame for closing'said second switch and holding said first switch in closed position, and means controlled by said last named temperature responsive means for deenergizing said electrica1 heating device.

4. In a fiuid fuel burner control system, a main burner, a pilot burner comprising a tube through which fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coefficient of expansion, a heater closely associated with the tube adjacent the open end thereof, electrically controlled main and pilot burner valves, first and second switches, a valve opening circuit for th pilot burner valve controlled by said first switch, a valve opening circuit for the main burner valve controlled by said second switch, means responsive to the expansion of the pilot burner tube for closing the first switch when the temperature of the tube as measured by its expansion is sufficient for the tube to be capable by itself of igniting the fuel passing therethrough as soon as it engages the atmosphere, and means responsive to the temperature of the pilot burner flame for closing said second switch and holding said first switch in closed position. 4

5. In a fluid fuel burner control system, a main burner, a pilot burner comprising a tube through which fuel passes before being admitted to the zon of combustion, said tube being of a material having an appreciable temperature coefficient of expansion, an electrical heater closely associated with the tube adjacent the open end thereof, electrically controlled main and pilot burner valves, first and second switch, a valve opening circuit for .the pilot burner valve controlled by said first switch, a valve opening circuit for the main burner valve controlled by said second switch, means responsive to the expansion of the pilot burner tube for closing the first switch when the temperature of the tube as measured by its expansion is sufficient for the tube to be capable by itself of igniting the fuel passing therethrough as soon as it engages the atmosphere, means responsive to the tempera ture of the pilot burner flame for closing said second switch and holding said first switch in closed position, and means controlled by said last named temperature responsive means for deenergizing said electrical heater.

6. In a fiuid fuel burner control system, a main burner, a pilot burner comprising a tube through which fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coeflicient of expansion, an electrical heater clomly cuit for the main burner valve controlled by said second switch, means responsive to the expansive of the pilot burner tube for closing the first switch, means responsive to the temperature of the pilot burner fiame for closing said second switch and holding said first switch in closed position, and means operative upon the opening of said main burner valve to deenergize said electrical heater.

7. In a fiuid fuel burner control system, a main burner, a pilot burner comprising a tube through which fuel passes before being admitted to the zone of combustion, an electrical heater closely associated with the tube adjacent the open end thereof, electrically controlled main and pilot burner valves, first and second switches, a valve opening circuit for the pilot burner valve controlled by said first switch, a valve opening circuit for the main burner valve controlled by said second switch, means responsive to the temperature of the pilot burner tube for closing the first switch, means responsive to the temperature of the pilot burner fiame for closing said second switch and holding said first switch in closed position, and means controlled by said last named temperature responsive means for deenergizing said electrical heater.

8. In combination, a fluid fuel burner comprising a tube through which the fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coefilcient of expansion, means adjacent the open end of said tube for heating it and the fuel passing therethrough to a temperature sufiiciently high that said fuel will ignite as soon as it contacts the air, andmeans including a device responsive to the expansion of the tube for preventing the supply of fuel to the burner except when the expansion of the tube indicates that the tube has reached said ignition temperature.

9. In combination, a fiuid fuel burner comprising a tube through which the fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coemcient of expansion, an electrical heating coil adjacent the open end of said tube for heating it and the fuel passing therethrough to a temperature sufilciently high that said fuel will ignite as soon as it contacts the air, a projection onsaid tube, a bell-crank :lever having one arm lying in the path of movement of said projection and a second arm fiexibly supporting two switch contacts, two stationary contacts mounted for cooperation with said lever arm contacts, a thermostatic element exposed to the flame of said burner and connected to a member extending in operative proximity to said second lever am. said projection'belng effective upon expansion of said tube corresponding to said ignition temperature to actuate said lever and cause engagement of one pair of said contacts, said thermostatic element being elective upon ignition of said burner fiame to move said member against said second lever arm and fiex the same so as to cause engagement of the second pair of said contacts, an electrically controlled supply valve for said bumer, an opening circuit for said valve controlled by said first pair of contacts, and a circuit including means to deenergize said heating coil controlled by said second pair of contacts.

10. In a fiuid fuel burner control system, a main fiuid fuel burner, a pilot burner including a tube having a fuel passage therethrough, electrical means for heating said passage, a device responsive to the temperature of said tube, means including said device for admitting fuel to said passage when said temperature is sufficient to cause ignition of the fuel passing through as soon as it engages the atmosphere, and means including a device responsive to the temperature of the pilot burner flame operative upon ignition of fuel fiowing from the pilot burner to admit fuel to the main burner.

11. In combination, a fiuid fuel burner including a tube having a fuel passage therethrough, electrical means for heating said passage, a device responsive to the temperature of said tube, and mean including said device for admitting fuel to said passage when said temperature is sufiicient to cause ignition of the fuel passing through as soon as it engages the atmosphere.

12. In combination, a fluid fuel burner comprising a tube through which the fuel passes before being admitted to the zone of combustion, said tube being of a material having an appreciable temperature coefficient of expansion, means adjacent the open end of said tube for heating it and the fuel passing therethrough to a temperature suiiiciently high that said fuel will ignite as soon as it contacts the air, a pro- Jection on said tube, a lever having one arm lying in the path of movement of said projection and a second arm for operating a switch, a valve controlling the fiow of fuel to said burner, an electrical operator for said valve, and an energizing circuit for said operator controlled by said switch.

FREDERICK S. DENISON. 

